"Great scenic shots" would be a plus point.
"Small cast" would make it look a bit odd.
The Camino de Santiago has a cast of thousands, and that's one of my abiding memories of the trail. With 300 people per day joining the trail in the peak summer period, and with lots more joining for shorter treks the closer you get to Santiago, it really does get very busy. For it to look 'authentic', it would really need lots of 'extras' shuffling along in the background, regardless of what the film's main characters were doing.
Oh... and it would need a noticeable number of Koreans too. Ever since the Korean journalist Suh Myung Sook wrote about the Camino de Santiago in 2006, everyone has commented on the number of Koreans now walking the route!